A traditional analog facsimile (or “fax”) generally involves the transmission of scanned-in printed material (e.g., text, photographs, or the like), usually to a telephone number associated with a printer or other output device via a public switched telephone network (PSTN), as specified, for example, in the International Telecommunication Union (ITU) T.30 standard (see, e.g., ITU-T Recommendation T.30, Procedures for Document Facsimile Transmission in the General Switched Telephone Network, SERIES T: TERMINALS FOR TELEMATIC SERVICES, September 2005, the disclosure of which is incorporated by reference herein in its entirety). After a call is established between a source facsimile machine and a receiving facsimile machine, the two machines are synchronized to each other, an original source document is scanned in by the source facsimile machine that treats the contents as a single fixed graphic image and converts the image into a bitmap. Once in this digital form, the information is transmitted as audio-frequency signals through the telephone system. The receiving facsimile machine converts the coded image to print a paper copy of the document. Alternatively, computers can be used as the source or receiving facsimile machine in which the originating document and the received copy of the document are stored electronically.
Instead of using the PSTN, voice transmission of voice over the Internet using Voice over Internet Protocol (VoIP) technology is becoming popular. Concomitantly, it is desirable to use the same Internet Protocol (IP) network used to transmit VoIP traffic for facsimile communication by connecting traditional analog facsimile machines to the IP network and using Facsimile over Internet Protocol (FoIP) technology specified, for example, in the International Telecommunication Union (ITU) T.38 standard (see, e.g., ITU-T Recommendation T.38, Group 3 Protocols, Procedures for Real-time Group 3 Facsimile Communication Over IP Networks, SERIES T: TERMINALS FOR TELEMATIC SERVICES, FACSIMILE, April 2007, the disclosure of which is incorporated by reference herein in its entirety).
The T.38 fax protocol supports the transmission of facsimile data across an IP network in real time, much like the original Group 3 (G3) fax standards did for PSTN. In this manner, T.38 preserves the traditional fax environment and yet allows faxes to be successfully sent and received by dynamically adjusting the transmitted fax signal to compensate for jitter, latency, and packet loss, which are common in the IP network. Without T.38, fax devices, which are sensitive to timing, would otherwise experience difficulty reliably sending and receiving faxes over an IP network. However, while the T.38 fax protocol addresses some of the problems associated with sending and receiving faxes in real-time over a packet network, several problems remain.